Up till now, the evaluation of the endocannabinoid system (ECS) in humans needs invasive procedures. The investigators managed in the lab to determine the levels of endocannabinoids in a small number of subjects. The aim of the study is to confirm that salivary is a useful tool to evaluate the activity of the ECS both in normal weight and obese subjects that are characterised by a hyperactivity of the system. Therefore, the first objective of the study is to compare the fasting level of salivary anandamide between 12 obese patients and 12 normal weight subjects.